In open-end spinning machines, it has been long known to seat the rotor shaft of the spinning rotor in the bearing wedge of a support disk bearing having two pairs of support rollers, since such bearings make possible very high rpm and have a long service life.
With support disk bearings of this type, the axes of the pairs of support rollers are customarily arranged slightly crossed, so that during operation an axial force component acts on the rotor shaft. This axial force component maintains the rotor shaft securely in contact with a mechanical axial bearing arranged at the end of the rotor shaft.
Although such rotor bearing as above described, and for example more fully disclosed in German Patent Publication DE 25 14 734 C2, has proven itself in actual use and large numbers thereof are in use, this type of rotor seating also has some disadvantages.
Not only is the spinning rotor limited to a structurally predetermined direction of rotation because of the crossed arrangement of the pairs of support disks, but the crossed arrangement of the pairs of support disks also results in increased friction in the area of the support disks/rotor shaft with the result, that the bearing faces of the support disks become heated. The coatings of the support disks are greatly stressed by this frictional heat, but additional energy is also required for overcoming this friction.
Furthermore, with this type of seating of the rotor shaft, the mechanical axial bearing arranged at the end of the rotor shaft is highly stressed, which has a negative effect on the service life of this bearing.
Although it has been possible to quite clearly improve the wear resistance of such axial bearings by the installation of a wear- resistant ceramic pin (as disclosed in German Patent Publication DE 41 17 174 A1), it continues to be necessary to sufficiently lubricate these bearings regularly. However, in spinning mills such bearings lubricated with oil are not without problems because of the almost unavoidable oil leaks.
A rotor bearing is known from the subsequently published German Patent Publication DE 197 29 191.0, which avoids the above described disadvantages. Although with this type of bearing, the rotor shaft of the spinning rotor is also seated in the bearing wedge of a support disk bearing, the axes of the two pairs of support disks are not crossed, but are arranged parallel with the rotor shaft and with one another. Thus, little or no axial forces act on the rotor shaft of the spinning rotor during operation. Instead, the axial positioning of the spinning rotor in the bearing wedge of the support disk bearing is provided by means of a magnetic bearing arranged at the end of the rotor shaft and having radially arranged magnetic bearing components. The special structural design of this magnetic bearing assures that the spinning rotor remains securely positioned even at rpm which are clearly greater than 100,000 revolutions per minute.
Because of its reduced energy requirements and increased service life, the support disk bearing in accordance with German Patent Publication DE 197 29 191.0 has indisputable advantages over support disk bearings with crossed pairs of support disks and mechanical axial bearings. Nevertheless, problems can arise when these support disk bearings are used, particularly in spinning mills in which open-end spinning devices with mechanical axial bearings as well as open-end spinning devices with magnetic rotor positioning are used. That is, the accidental installation of a rotor designed for a mechanical bearing in an axial thrust-free open-end spinning device with magnetic positioning of the spinning rotor can cause considerable damage to the respective spinning device because of the lack of an axial fixation of the spinning rotor which would then occur. In addition, such a spinning rotor installed in the wrong spinning device, which therefore is not fixed in its axial direction, represents a not inconsiderable risk of an accident, especially because of its high operating rpm.
A sufficient and dependable fixation of the rotor shaft in the bearing wedge of the support disk bearing, particularly when operating at high rpm, is only assured when the bearing components involved, i.e. the bearing component which has the permanent magnets and is arranged stationarily on the spinning device and the bearing component rotating with the bearing shaft, are exactly matched to each other. Thus, even small deviations of the bearing components can result in considerable damage.